Generate a Typescript interface from an OpenApiSpex Schema struct

typescript_interface_generator.ex

defmodule MoxleyApiUtil.TypescriptInterfaceGenerator do
  alias OpenApiSpex.Schema

  def to_ts_interface(%Schema{type: :object} = schema) do
    header = "interface #{schema.title} {"
    body = Enum.map(schema.properties, &to_ts_property_line/1) |> Enum.join("\n")
    header <> "\n" <> body <> "\n}\n"
  end

  defp to_ts_property_line({name, schema}) do
    ts_type = to_ts_type(schema)
    "  #{name}: #{ts_type};"
  end

  defp to_ts_type(module) when is_atom(module) do
    to_ts_type(module.schema())
  end

  defp to_ts_type(%{type: :object} = schema) do
    to_ts_interface(schema)
  end

  defp to_ts_type(%{type: :string, format: :datetime}) do
    "Date"
  end

  defp to_ts_type(%{type: :string, enum: [_ | _] = enum}) do
    enum |> Enum.map(&Jason.encode!/1) |> Enum.join(" | ")
  end

  defp to_ts_type(%{type: type}) do
    type
  end
end